This invention relates to the production of sheet materials and, more particularly, to the provision of rounded corners on sheets cut from a web.
It is known and generally accepted that sheet materials such as X-ray films and punch cards should have rounded corners. It is also known that such corners can be provided by notching the sides of a running web and then cutting the web at the center of the notches. The difficulty with this mode of corner-rounding is that of lining up the cutters with the notches. Any failure to center the cut precisely on the notch leaves sharp strips of material on one of the sheets and an incomplete corner on the other. Another known mode involves stopping the process while the sheet just cut from the web is positioned and its corners rounded. Obviously, this presents a serious limitation on productivity. Still another mode involves cutting sheets from a web, stacking a predetermined number of the sheets and then moving the stack to off-line equipment which has cutters for corner-rounding the stacked plurality of sheets. In addition to costs of handling and equipment, difficulties have been encountered due to misalignment of individual sheets in their stacks.